Aliphatic polyester film and gas barrier film

ABSTRACT

A film of the present invention includes, as its main component, an aliphatic polyester whose primary repeating unit is represented by a general formula —O—CHR—CO— (where R denotes H or an alkyl group having a carbon number of 1-3). A three-dimensional surface roughness SRa of at least one side of the film is about 0.01 μm to about 0.1 μm. PCC value denoting the number of projections on the film per a unit of area along a mean roughness plane and the three-dimensional surface roughness SRa satisfy the following relationship: PCC value≦7000-45000×SRa.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a novel aliphaticpolyester film.

[0003] In the first aspect, the present invention relates to analiphatic polyester film having a desirable handling property,transparency, and adhesiveness, which is particularly suitable forpackaging applications.

[0004] In the second aspect, the present invention relates to analiphatic polyester film having a desirable suitability for processessuch as printing and laminating processes, which is an importantproperty of a packaging film for use with fresh food, processed food,drugs, medical devices, electronics, or the like, and also having adesirable heat seal strength after being made into a bag.

[0005] In the third aspect, the present invention relates to a novelaliphatic polyester film having a desirable suitability for processessuch as printing and laminating processes.

[0006] In the fourth aspect, the present invention relates to a gasbarrier film and, more particularly, to a gas barrier film which hasdesirable transparency, flexibility, running property during the filmprocessing (i.e., the capability of smoothly running through thefilm-forming machine), and gas barrier property after the film has runthrough a film processing machine while being in contact with a partthereof. These are important properties required in a packaging film foruse with fresh food, processed food, drugs, medical devices,electronics, or the like.

[0007] 2. Description of the Related Art

[0008] Conventionally, various plastic materials such as a polyolefin(e.g., polyethylene, polypropylene), an aromatic polyester (e.g.,polyethylene terephthalate), and a polyamide (e.g., nylon 6) have beenused in packaging films for packaging various items such as food. Usedpackaging films are supposed to be collected, and either incinerated orburied underground. However, such collection requires a lot of effort.Therefore, as we know, some used packaging films are in fact leftuncollected, creating various problems such as environmental pollution.When used films are incinerated, an excessively large heat is oftengenerated which significantly damages the furnace, while theincineration requires a large amount of fuel and thus a high cost. Whenburied underground, on the other hand, used films, which are notbiodegradable, remain in the soil on a semipermanent basis. In view ofthe current situations as described above, there is an increasing demandfor a general-purpose packaging film which has a desirablebiodegradability.

[0009] In order to provide a biodegradability to a polyethylene, or thelike, various methods have been devised in the art in which a componenthaving a biodegradability, e.g., starch, is blended with the film.Moreover, a method of providing a photo-degradability, and a method ofblending a polyethylene provided with a photo-degradability and a starchcomponent having a biodegradability, have been devised in the art. Thesemethods have attracted public attention as methods which may possiblysolve the above-described problems. With such methods, however, whilethe starch component having a biodegradability is degraded bymicroorganism, polymer components other than the starch are notdegraded, thereby failing to completely solve the above-describedproblems.

[0010] Thus, along with the increasing public concern for environmentalprotection, there has been a demand for a plastic product which, whendisposed in the natural environment, degrades or disappears over timewithout adversely affecting the natural environment.

[0011] In order to provide a complete solution to the above-describedproblems, various biodegradable polymer materials in which the polymeritself has a biodegradability have been devised in the art.Particularly, various polylactic acid materials have been activelydeveloped in the art because a polylactic acid easily degrades whendisposed in the natural environment. For example, a polylactic acid filmis naturally hydrolized in the soil and then degraded by microorganismsinto an environmentally harmless substance. For example, a polylacticacid film has been used in medical molded products (Japanese Publicationfor Opposition No. 41-2734, Japanese Publication for Opposition No.63-68155, etc.), as well as in basic materials of other general-purposedisposable materials which are biodegradable.

[0012] Particularly, a biaxially drawn aliphatic polyester film isexpected to be used in a wide variety of applications such as generalpackaging materials, because it has a transparency, a biodegradability,as well as mechanical properties comparable to those of commonly usedfilms.

[0013] For example, Japanese Laid-Open Publication No. 7-207041describes a biodegradable film having a practically acceptable strengthand thermal dimensional stability, which is made of a polylacticacid-based polymer, and in which the degree of plane orientation Δp isabout 3.0×10⁻³ or more, and (ΔHm−ΔHc) is about 20 J/g or more, which isthe difference between the amount of crystallization melting heat ΔHmresulting when heating the film and the amount of crystallization heatΔHc resulting from the crystallization during the heating.

[0014] However, these films have the following problems.

[0015] The first problem is as follows. Generally, a film is required tohave a take-up property during a film-forming process, and aslipperiness during use. When the slipperiness is insufficient, thehandling property during film production and film processingdeteriorates. Due to the low slipperiness, the tension on the filmincreases while the film is running in contact with a guide roll, or thelike, resulting in a frictional flaw on the film surface, therebylowering the running property. Japanese Laid-Open Publication Nos.8-34913 and 9-278997 disclose methods for improving the slipperiness andthus the handling property of a film. The improvement is provided byadding, to a film, an organic slip additive such as a fatty acidester-based slip additive, a fatty acid-based slip additive, a fattyacid amide-based slip additive, as well as an inorganic minute particleanti-blocking agent such as silica and calcium carbonate.

[0016] However, when used in a packaging bag, a polylactic acid filmneeds to be laminated by a heat seal with a sealant film such as apolyolefin. With the addition of the organic slip additive as describedin Japanese Laid-Open Publication Nos. 8-34913 and 9-278997 toapolylactic acid film in order to improve the handling property, therunning property is improved, but the adhesion strength between thepolylactic acid film and a sealant is reduced. Then, it is difficult touse such a film as a packaging bag because of the insufficient adhesion.

[0017] Thus, it has been difficult to improve the process suitabilitysuch as the printing process suitability or the handling property, whichis required for a package film, while also improving the adhesiveness atthe heat seal portion after the film is made into a bag, by the additionof only the above-described slip additive or the anti-blocking agent.

[0018] The second problem is as follows. The above-described polylacticacid-based film has been developed while preferentially improving thedegradability in the natural environment. Consequently, the desirableproperties inherent to an aliphatic polyester have not been sufficientlyretained. In other words, the orientation and the crystallization of thefilm, as well as the strength and the thermal dimensional stability,have not been sufficient, because of the preferential improvement in thebiodegradability thereof.

[0019] It has been found that, when used as a packaging film for freshfood, processed food, drugs, medical devices, electronics, or the like,such a film may experience a change in dimension or wrinkling inprocesses such as a printing process or a laminating process which arerequired for a packaging film.

[0020] The third problem is as follows. A polylactic acid film has arelatively high gas permeability. Thus, when a polylactic acid film isused in a food packaging material, there is a vital problem ofshortening the storage period of the food packaged therein.

[0021] Japanese National Phase PCT Laid-Open Publication No. 8-505825provides a solution to this problem by applying a vapor-deposited filmof a metal such as aluminum on a film. However, a film obtained by thismethod has a reduced transparency, while the transparency of the film isrequired particularly in food packaging applications, and thus has seena limited variety of applications.

[0022] In order to solve the problem, Japanese Laid-Open Publication No.10-138433, Japanese Laid-Open Publication No. 10-24518, etc., propose apolylactic acid-based gas barrier film on which a vapor-deposited filmof an inorganic oxide having a transparency is applied. While such a gasbarrier film improves the transparency, the running property during thefilm processing and the gas barrier property after the film has runthrough a film processing machine while being in contact with a partthereof are not sufficient.

SUMMARY OF THE INVENTION

[0023] According to one aspect of this invention, a film includes, asits main component, an aliphatic polyester whose primary repeating unitis represented by a general formula —O—CHR—CO— (where R denotes H or analkyl group having a carbon number of 1-3). A three-dimensional surfaceroughness SRa of at least one side of the film is about 0.01 μm to about0.1 μm. PCC value denoting the number of projections on the film per aunit of area along a mean roughness plane and the three-dimensionalsurface roughness SRa satisfy the following relationship: PCCvalue≦7000-45000×SRa.

[0024] In one embodiment of the invention, the PCC value is about1000/mm² or more.

[0025] In one embodiment of the invention, the aliphatic polyester is apolylactic acid.

[0026] According to another aspect of this invention, a film includes,as its main component, an aliphatic polyester whose primary repeatingunit is represented by a general formula —O—CHR—CO— (where R denotes Hor an alkyl group having a carbon number of 1-3). A refractive index(Nz) in a thickness direction thereof is about 1.440 to about 1.455. Asurface energy of the film is about 45 dyne/cm or more.

[0027] In one embodiment of the invention, the film further includes aresin layer having a heat seal property.

[0028] In one embodiment of the invention, the resin layer having a heatseal property includes a polyolefin resin.

[0029] In one embodiment of the invention, the aliphatic polyester is apolylactic acid.

[0030] According to still another aspect of this invention, a filmincludes, as its main component, an aliphatic polyester whose primaryrepeating unit is represented by a general formula —O—CHR—CO— (where Rdenotes H or an alkyl group having a carbon number of 1-3). A thicknessunevenness along a longitudinal direction of the film is about 10% orless. A thermal shrinkage along the longitudinal direction at about 120°C. is about 5% or less.

[0031] In one embodiment of the invention, a refractive index (Nz) alonga thickness direction of the film is about 1.440 to about 1.455. Thethermal shrinkage along the longitudinal direction at about 120° C. isabout 3% or less.

[0032] In one embodiment of the invention, a value (Nx−Ny), which isobtained by subtracting a refractive index (Ny) in a width direction ofthe film from the refractive index (Nx) in the longitudinal directionthereof, is about −0.020 to about 0.

[0033] In one embodiment of the invention, a weight average molecularweight of the aliphatic polyester is about 10000 to about 500000.

[0034] In one embodiment of the invention, the aliphatic polyester is apolylactic acid.

[0035] According to still another aspect of this invention, a gasbarrier film includes a resin layer and a vapor-deposited layer which isapplied on at least one side of the resin layer. The resin layerincludes, as its main component, an aliphatic polyester whose primaryrepeating unit is represented by a general formula —O—CHR—CO— (where Rdenotes H or an alkyl group having a carbon number of 1-3). Thevapor-deposited layer is selected from the group consisting of analuminum oxide/silicon oxide-based vapor-deposited layer, an aluminumoxide-based vapor-deposited layer and a silicon oxide-basedvapor-deposited layer. A content of aluminum oxide in the aluminumoxide/silicon oxide-based vapor-deposited layer is about 20 wt % toabout 99 wt %. A “b” value, which is calculated according to thefollowing expression (1) based on a specific gravity D of thevapor-deposited layer and the aluminum oxide content A in wt % in thevapor-deposited layer, satisfies the following expression (2):

[0036] Expression (1): b=D−0.01A

[0037] Expression (2): 1.6≦b≦2.2

[0038] (where D denotes the specific gravity of the vapor-depositedlayer, and A denotes the aluminum oxide content in wt % in thevapor-deposited layer). A specific gravity of the aluminum oxide-basedvapor-deposited layer is about 2.70 to about 3.30. A specific gravity ofthe silicon oxide-based vapor-deposited layer is about 1.80 to about2.20.

[0039] In one embodiment of the invention, a three-dimensional surfaceroughness SΔa (a three-dimensional average inclination gradient) of atleast the deposition side of the resin layer is about 0.01 to about0.04. Substantially no projection as high as about 1.89 μm or moreexists on at least the deposition side of the resin layer.

[0040] In one embodiment of the invention, a thickness of the resinlayer is about 10 μm to about 250 μm. A thickness of the vapor-depositedlayer is about 10 Å to about 5000 Å.

[0041] In one embodiment of the invention, the aliphatic polyester is apolylactic acid.

[0042] Thus, the invention described herein makes possible theadvantages of (1) providing an aliphatic polyester film useful as ageneral-purpose packaging film; (2) providing a biaxially drawnaliphatic polyester film having a desirable handling property,transparency and adhesiveness, which is particularly suitable forpackaging applications; (3) providing a novel aliphatic polyester filmhaving a desirable suitability for processes such as printing andlaminating processes; and (4) providing a gas barrier film, which solvesthe above-described conventional problems in films and layered films,thereby being useful in general-purpose films by providing a desirabletransparency, a desirable flexibility, a desirable running propertyduring the film processing, and a desirable gas barrier property afterthe film has run through a film processing machine while being incontact with a part thereof.

[0043] These and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] “Aliphatic polyester” as used herein refers to a polyester whoseprimary repeating unit is represented by the general formula —O—CHR—CO—(where R is H or an alkyl group having a carbon number of 1-3).

[0045] While it is preferred that all of the repeating units in thealiphatic polyester are represented by the above general formula, otherunits which are not represented by the above general formula may also beincluded to an extent such that the properties of an aliphatic polyesterare retained. For example, preferably about 70% or more, more preferablyabout 80% or more, even more preferably about 90% or more, and mostpreferably about 95% or more, of the repeating units in the molecule arethose represented by the above general formula.

[0046] While an aliphatic polyester does not normally include anaromatic component, an aromatic component may employed to an extend suchthat the properties of the aliphatic polyester are retained. In such acase, preferably about 10 mol % or less, more preferably 5 mol % orless, and even more preferably 3 mol % or less, of the repeating unitsin the molecule are those including an aromatic structure.

[0047] Specific examples of the aliphatic polyester include, though arenot limited to, a polylactic acid, a polyglycol acid, and apoly(2-oxyhydroxybutyric acid). A polylactic acid is currently mostpreferred in terms of performance and cost. The aliphatic polyester maybe a homopolymer, or a copolymer of more than one of the repeating unitsselected from the group defined by the above-described general formula.Moreover, the aliphatic polyester may be a single polymer, or a mixtureof more than one types of aliphatic polyesters.

[0048] When the carbon atoms forming the aliphatic polyester include anyasymmetric carbon, there may exist optical isomers such as L-isomer,DL-isomer and D-isomer. Any of these optical isomers may be employedalone or as a mixture of two or more.

[0049] Moreover, other polymer materials may be mixed in the aliphaticpolyester to an extent such that the desirable effects provided by thepresent invention are not inhibited. Where another polymer material ismixed in the aliphatic polyester, preferably about 70 wt %, morepreferably about 80 wt %, even more preferably about 90 wt %, and mostpreferably about 95 wt %, of the total weight of the aliphatic polyestertogether with the other polymer material is aliphatic polyester.

[0050] The above-described aliphatic polyester (hereinafter, alsoreferred to simply as “the polymer”) may be produced as a material of afilm of the present invention by using any appropriate method known inthe art, e.g., a ring-opening polymerization of an anhydrous cyclicester compound of a corresponding α-oxy acid.

[0051] The weight-average molecular weight of the above-describedaliphatic polyester is preferably about 5000 to about 500000, morepreferably about 10000 to about 500000, even more preferably about 40000to about 300000, and most preferably about 50000 to about 300000. Whenthe weight-average molecular weight is excessively low, the propertiesof an obtained biodegradable layered film are easily deteriorated, andthe biodegradation speed tends to be too high. The weight-averagemolecular weight is preferably about 10000 or more in order tosufficiently ensure the extrudability from a film-forming machine andthe drawability in a biaxial drawing machine. On the other hand, whenthe weight-average molecular weight is excessively high, the meltingextrusion of the aliphatic polyester is difficult.

[0052] As necessary, any additive known in the art can be added to theabove-described aliphatic polyester. For example, a slip additive, ananti-blocking agent, a thermal stabilizer, an antioxidant, an antistaticagent, a light-resistance agent, a shock resistance improver, acrystalline nucleus agent, an anti-coloring agent, a pigment, a dye, anultraviolet absorber, a mold releasing agent, a slip-promoting agent, aflame retarder, and the like, may be added. For example, one or more ofthe following may be added as necessary in view of the antistaticproperty, etc.: an anionic surfactant such as a laurylphosphatepotassium salt; a cationic surfactant such as a quaternary ammoniumsalt; a nonionic surfactant such as an aliphatic higher alcohol or anethyleneoxide added higher aliphatic acid; a polyalkylene glycol such asa polyethylene glycol or a polyethylene glycol/polypropylene glycolblock copolymer; and a silicone oil such as dimethylpolysiloxane,polyether denatured silicone oil, or a higher alkoxy denatured siliconeoil. Moreover, one or more of the following may be added to thealiphatic polyester as necessary in order to variously adjust themechanical properties, the biodegradability, etc.: a polymer such as apolyamino acid, or the like, an inorganic substance such as talc,calcium carbonate, calcium sulfate, calcium chloride, or a siliconoxide, starch, a protein, a food additive, and the like.

[0053] However, where the aliphatic polyester film is used in atransparent film application (e.g., in the fourth aspect of the presentinvention), the layered film on which a vapor-deposited layer of anoxide is deposited needs to be transparent so that the contents thereincan be seen therethrough. Therefore, the types of additives to be addedshould be selected so that the film has a high transparency beforeapplying the vapor-deposited layer.

[0054] For example, an inorganic particle, an organic salt particle or across-linked polymer particle may be added as a slip additive to thealiphatic polyester.

[0055] Specific examples of inorganic particles include a metal oxidesuch as silica, titanium dioxide, aluminum oxide, silicon oxide, andzirconium oxide, a metal salt such as calcium carbonate, calciumphosphate, kaolinite, kaoline, talc, magnesium carbonate, bariumcarbonate, calcium sulfate, lithium phosphate, calcium phosphate,magnesium phosphate, lithium fluoride, and barium sulfate.

[0056] Particularly, a silica particle aggregate of primary particles ispreferably used as an inorganic particle for obtaining a film having adesirable handling property along with a low haze.

[0057] Specific examples of organic salt particles include calciumoxalate, or a terephthalate of calcium, barium, zinc, manganese,magnesium, or the like.

[0058] Specific examples of cross-linked polymer particles include apolymer or copolymer of a vinyl-based monomer such as divinylbenzene,styrene, acrylic acid, or methacrylic acid. More specifically, anorganic polymer such as a cross-linked polystyrene resin, a cross-linkedacrylic resin, and a cross-linked polyester resin may be used. Moreover,other organic particles such as polytetrafluoroethylene, abenzoguanamine resin, a thermosetting epoxy resin, an unsaturatedpolyester resin, a thermosetting urea resin, a thermosetting phenolresin, or a silicone resin may be used.

[0059] Such particles may be used preferably because they are inert toan aliphatic polyester.

[0060] Such slip additives may be used alone or in combinations of twoor more. The average particle size of the slip additives used ispreferably about 0.01 μm to about 3.0 μm, and more preferably about 0.05μm to about 2.5 μm. In order to improve both the transparency and theslipperiness of the film, the amount of the slip additive to be added ispreferably about 0.005 wt % to about 2 wt %, and more preferably about0.01 wt % to about 1.0 wt of the total film composition.

[0061] In order to improve both the transparency and the slipperiness,it is preferred to use two or more slip additives in combination.Particularly, it is preferred to use a slip additive particle whichdeforms during the film formation (e.g., an organic slip additive havinga low degree of cross link such as a cross-linked polystyrene resin or across-linked acrylic resin, or an inorganic slip additive such as asilica which is an aggregate of primary particles) in combination withanother slip additive particle which does not deform during the filmformation.

[0062] The method for adding the above-described slip additive to thealiphatic polyester is not limited to any particular method, but anyappropriate method known in the art may be used. In the case where apolylactic acid is used as the aliphatic polyester, exemplary methodsinclude those in which a slip additive is dispersed in a melted lactidebefore polymerization of the lactide, and those in which a slip additiveis dispersed during the polymerization reaction of the lactide.

[0063] Film Formation Method

[0064] The aliphatic polyester composition thus prepared can be formedinto a film by any appropriate method known in the art. After the filmformation, the film is preferably further drawn by, for example, anuniaxial drawing method in which the film is drawn in either vertical orlateral direction, an inflation method, or a biaxial drawing method suchas a simultaneous biaxial drawing method or a successive biaxial drawingmethod. When using the successive biaxial drawing method, either thevertical drawing step or the lateral drawing step may be performedfirst. Moreover, various other drawing methods such as alateral/vertical/vertical drawing method, a vertical/lateral/verticaldrawing method, and a vertical/vertical/lateral drawing method mayalternatively be used. As necessary, the film may be further subjectedto a thermofixing process, a vertical relaxation process or a lateralrelaxation process. More preferably, the film is thermally fixed afterthe biaxial drawing.

[0065] For example, the film may be biaxially drawn and then thermallyfixed after being formed by an extrusion machine.

[0066] For example, when an aliphatic polyester film is produced by anextrusion molding method, a T-die method or an inflation method, whichare known in the art, may be used so as to obtain an undrawn film. Theextrusion temperature may be about Tm to about Tm+70° C., and morepreferably about Tm+20° C. to about Tm+50° C., where Tm is the meltingtemperature of the biodegradable aliphatic polyester used. When theextrusion temperature is excessively low, it may be difficult to stablyperform the extrusion molding because of an excessive load applied tothe extrusion machine. When the extrusion temperature is excessivelyhigh, the aliphatic polyester is undesirably easily degraded. The die ofthe extrusion machine used for producing the aliphatic polyester filmmay be those having circular or linear slits. Moreover, the temperatureof the die may be substantially equal to the extrusion temperature.

[0067] The biaxial drawing of an undrawn film of the aliphatic polyestermay be done by successively performing two drawing steps one along thefirst axis direction and another along the second axis direction, or bysimultaneously performing two drawing steps.

[0068] The drawing temperature is preferably about Tg to about Tg+50°C., and more preferably about Tg+10° C. to about Tg+40° C., where Tg isthe glass-transition temperature of the aliphatic polyester used. Whenthe drawing temperature is excessively low, the drawing process isdifficult to perform. When the drawing temperature is excessively high,the uniformity in thickness and the mechanical strength of the obtainedfilm may undesirably be reduced.

[0069] Each of the vertical and lateral drawing processes may beperformed in a single stage or in a plurality of stages. In any case, interms of the uniformity in thickness and the mechanical properties, itis preferred to finally achieve a drawing ratio of about 3 or more, andmore preferably about 3.5 or more, in either drawing direction, or adrawing ratio in area of about 9 or more, and more preferably about 12or more. When the vertical or lateral drawing ratio is about 3 or less,or 9 or less in area, it may be difficult to obtain a film having adesirable uniformity in thickness, or to sufficiently improve theproperties such as the mechanical strength. The thickness of the resinlayer whose main component is an aliphatic polyester is normally about10 μm to about 250 μm, and preferably about 12 μm to about 250 μm.

[0070] Herein, the longitudinal direction in a biaxially drawn filmrefers to the vertical drawing direction, while the width directionrefers to the lateral drawing direction.

[0071] The upper limit of the drawing ratio is not limited to anyparticular ratio, though it is preferred to control the drawing ratio sothat the film will not be ruptured during the drawing process.

[0072] The aliphatic polyester film may be produced as a multilayer filmby using a coextrusion process with another resin or providing anadditional coating process.

[0073] For particular applications, a corona discharge treatment, acoating treatment, a plasma treatment, or a flame treatment, may beperformed in order to improve the surface energy of the aliphaticpolyester film or to improve the adhesiveness or the wettabilitythereof. Particularly, before an oxide vapor-deposited layer isdeposited on the film, the above-described treatment may be performed inadvance so as to improve the adhesiveness between the film and the oxidevapor-deposited layer.

[0074] First Aspect of the Present Invention

[0075] According, to the first aspect of the present invention, thethree-dimensional surface roughness SRa of the biaxially drawn aliphaticpolyester film is about 0.01 μm or more. When the three-dimensionalsurface roughness SRa is less than about 0.01 μm, the handling propertywill be poor. When the three-dimensional surface roughness SRa is morethan about 0.1 μm, the transparency and/or the anti-erosion propertywill be poor.

[0076] Moreover, the number of projections per a unit of area (PCCvalue) along the mean roughness plane of the biaxially drawn aliphaticpolyester film is preferably about 1000/mm² or more. When the PCC valueis excessively low, the handling property or the running property arelikely to be poor.

[0077] When the PCC value is outside the following range: PCCvalue≦7000-45000×SRa, the transparency will be poor.

[0078] The PCC value denoting the number of projections along the meanroughness plane, and the three-dimensional surface roughness SRa, may beadjusted by controlling the film formation conditions and the slipadditive particles. The type of slip additive used and the amount of theslip additive added are not limited to any particular type or amount aslong as the PCC value and the three-dimensional surface roughness SRaare within predetermined ranges. Preferably, the slip additive is aninorganic particle. The average particle size of the slip additive ispreferably about 0.01 μm to about 5 μm, and more preferably about 1 μmto about 4 μm. The amount of slip additive added is preferably about0.01 wt % to about 0.8 wt %, and more preferably about 0.03 wt % toabout 0.5 wt %.

[0079] Herein, the mean roughness plane refers to a plane such that thetotal volume of upper portions of the protrusions on the film existingabove the plane is equal to the total volume of the space definedbetween lower portions of the protrusions on the film existing below theplane.

[0080] When the average particle size of the slip additive isexcessively small, it is difficult to control the three-dimensionalsurface roughness SRa to be about 0.01 μm or more. When the averageparticle size of the slip additive is excessively large, it is oftendifficult to control the PCC value to be about 1000/mm2 or more and thethree-dimensional surface roughness SRa to be about 0.1 μm or less. Whenthe amount of slip additive added is excessively small, it is difficultto control the PCC value to be about 1000/mm² or more and thethree-dimensional surface roughness SRa to be about 0.01 μm or more.When the amount of slip additive added is excessively large, it is oftendifficult to control the three-dimensional surface roughness SRa to beabout 0.1 μm or less.

[0081] As necessary, an organic slip additive, in addition to theabove-described slip additives, may be further added to the filmaccording to the first aspect of the present invention. As the organicslip additive, a hydrocarbon resin, a fatty acid ester, paraffin, ahigher fatty acid, aliphatic ketone, and a fatty acid amide, and thelike, are known in the art.

[0082] According to the first aspect of the present invention, it ispossible to provide the slipperiness by controlling the SRa value andthe PCC value, which are related to the surface profile of the film, tobe within predetermined ranges. Therefore, it may not be necessary toadd an organic slip additive. Moreover, the addition of an organic slipadditive often results in a bleed-out of the organic slip additiveacross the film surface. In such a case, the adhesion strength afterlaminating the film with a sealant film of a polyolefin, or the like, isoften insufficient. Therefore, it may be preferred not to add an organicslip additive.

[0083] According to the first aspect of the present invention, the filmdrawing conditions may vary depending upon the slip additive to beadded. The film drawing conditions are selected so that the PCC valuealong the mean roughness plane and the three-dimensional surfaceroughness SRa fall within predetermined ranges.

[0084] For example, where the film is first drawn in the verticaldirection in one or more stages and then drawn in the lateral direction,the refractive index (Nx) in the vertical direction after the verticaldrawing process is preferably about 1.555 or less. When Nx isexcessively large, the formation of the surface projections during theproduction process is often insufficient, whereby the handling propertyor the running property may be poor.

[0085] In a preferred embodiment of the present invention, a resin layerhaving a heat seal property, i.e., a sealant layer, is laminated on thealiphatic polyester film. A polyolefin resin, e.g., polypropylene andpolyethylene, is preferably used for the resin layer having a heat sealproperty.

[0086] As necessary, an adhesion improving layer may be deposited on thefilm of the present invention. The adhesion improving layer as usedherein refers to a layer which is provided on the aliphatic polyesterfilm for improving the adhesive strength between the aliphatic polyesterfilm and other various layers such as the sealant layer. The material ofthe adhesion improving layer may be any appropriate material which mayimprove the adhesive strength between the sealant layer and thealiphatic polyester film. For example, the material may be one selectedfrom a polyester, an acrylic resin, a polyurethane, and the like, or acopolymer (including a block copolymer and a graft copolymer) of two ormore selected therefrom.

[0087] An additive such as an antistatic agent, an in organic slipadditive, an ultraviolet absorber, an organic slip additive, anantibacterial agent, or a photo-oxidization catalyst, may be added tothe adhesion improving layer to an extent such that the desirableeffects provided by the present invention are retained. Such an additivemay be provided to the surface of the aliphatic polyester film byincluding the additive in a coating which contains a resin of theadhesion improving layer.

[0088] Any appropriate coating method known in the art such as a gravuremethod, a reverse method, a die method, a bar method, or a dip method,may be used for coating the aliphatic polyester film with a coatingmaterial containing the above-described adhesion-modifying material inorder to provide the adhesion improving layer.

[0089] The amount of coating solution (as a solid content) is preferablyabout 0.005 g/m² to about 10 g/m², and more preferably about 0.02 g/m²to about 0.5 g/m². When the amount of coating is excessively small, itis difficult to obtain a sufficient adhesive strength between thealiphatic polyester film and the sealant layer. When the amount ofcoating is excessively large, blocking, and other problems in practicaluse, are likely to occur.

[0090] The adhesion improving layer may be provided by coating thealiphatic polyester film with the above-described coating material.Alternatively, the adhesion improving layer may be provided by firstcoating an undrawn or uniaxially drawn aliphatic polyester film with theabove-described coating material, drying the coated film, and then, asnecessary, further uniaxially or biaxially drawing the resulting filmand thermally fixing the same.

[0091] Where the adhesion improving layer is laminated on the aliphaticpolyester film, a corona treatment, a flame treatment, a surfacetreatment using an electron beam irradiation may be performed in orderto further improve the adhesiveness of between the aliphatic polyesterfilm and the adhesion improving layer.

[0092] Where an undrawn or uniaxially drawn aliphatic polyester film iscoated with the above-described coating solution, dried, and furtherdrawn, the temperature at which the drying process is performed afterthe coating is adjusted so as not to affect the subsequent drawingprocess. By performing a thermofixing process at a temperature of about140° C. or more after the further drawing process, the coating film canbe made hard while dramatically improving the adhesiveness between theadhesion improving layer and the aliphatic polyester film.

[0093] The adhesion improving layer thus provided on the aliphaticpolyester film has a desirable adhesiveness with respect to variousmaterials. Still, in order to further improve the adhesiveness or theprinting property, the adhesion improving layer may be further subjectedto a surface treatment using a corona treatment, a flame treatment, oran electron beam irradiation.

[0094] The adhesion-facilitated aliphatic polyester film obtained by thefirst aspect of the present invention has a desirable adhesive strengthwith respect to various types of layers having various functions and maybe used in a wide range of applications. For example, the various typesof layers having various functions may include a photosensitive layer ina photograph, a diazo type photosensitive layer, a mat layer, a magneticlayer, an ink-jet ink receiving layer, a hard coat layer, a printing inkor UV ink receiving layer, an adhesive layer used when providing alaminated film by dry lamination or extrusion lamination, or the like, athin film layer used in electron beam deposition, sputtering, ionplating, CVD, plasma polymerization, or the like, and an organic barrierlayer.

[0095] Second Aspect of the Present Invention

[0096] According to the second aspect of the present invention, therefractive index in the thickness direction (Nz) may be adjusted by anyappropriate method to be within a predetermined range.

[0097] For example, a process in which the vertical drawing is performedin two or more stages, at least one of which is performed at atemperature of about Tg+20° C. to about Tg+40° C. and at a drawing rateof about 10000%/min, preferably about 15,000%/min, and more preferablyabout 20000%/min or more, may be used.

[0098] The refractive index in the thickness direction (Nz) of thealiphatic polyester film according to the second aspect of the presentinvention needs to be about 1.440 to about 1.455, and more preferablyabout 1.445 to about 1.455. When the value Nz is excessively small, thefilm may easily be ruptured during a film forming process, andwrinkling, planarity deterioration, and the like, may occur during aprinting, laminating or heat seal process, or the like, while the heatseal strength may be poor. When the value Nz is excessively large,wrinkling, planarity deterioration, elongation, or the like, may occurduring a printing, laminating or heat seal process, or the like, therebyreducing the process suitability of the film.

[0099] The film surface energy of the aliphatic polyester film accordingto the second aspect of the present invention is about 45 dyne/cm ormore, and preferably about 47 dyne/cm or more. When the surface energyis excessively small, the heat seal strength is likely to beinsufficient.

[0100] In a preferred embodiment of the present invention, a resin layerhaving a heat seal property, i.e., a sealant layer, is laminated on thealiphatic polyester film. A polyolefin resin, e.g., polypropylene,polyethylene, and the like, is preferably used for the resin layerhaving a heat seal property.

[0101] The heat seal layer contains a polyolefin resin as its maincomponent, and is deposited by a method such as dry lamination orextrusion lamination. In a method typically employed in dry lamination,the coating of an adhesive layer is done by a gravure coating method, areverse kiss roll coating method, or a reverse roll coating method.Then, the coated layer is dried, and then a polyolefin film having aheat seal property is laminated thereon. The adhesive used may be atwo-part urethane-based adhesive in which a base having an OH group ismixed with a curing agent having an NCO group, or other isocyanate-basedadhesives, etc. An exemplary polyolefin resin may be a polyethylene, apolypropylene, a copolymer thereof, or the like.

[0102] Third Aspect of the Present Invention

[0103] According to the third aspect of the present invention, thethickness unevenness and the thermal shrinkage may be adjusted by anyappropriate method.

[0104] For example, a process in which the vertical drawing is performedby two or more stages, at least one of which is performed at atemperature of about Tg+20° C. to about Tg+40° C. and at a drawing rateof about 10000%/min, preferably about 15000%/min, and more preferablyabout 20000%/min or more, may be used. The upper limit of the drawingrate is not limited to any particular rate as long as the formed filmwill not be ruptured.

[0105] In order to further reduce the thickness unevenness, it iseffective to perform, after the above-described biaxial drawing processand before the thermofixing process, a fixed-length heat treatment at atemperature of about Tg−10° C. to about Tg+40° C., more preferably aboutTg to about Tg+30° C. (where Tg is the glass-transition temperature ofthe biaxially drawn film) for about 1 second to about 600 seconds. Whenthe temperature of the heat treatment is excessively low, the effect ofthe heat treatment may not be sufficiently obtained. When thetemperature of the heat treatment is excessively high, it is oftendifficult to improve the thickness unevenness after the heat treatment,thereby rather increasing the thickness unevenness.

[0106] The mechanism by which the heat treatment, performed between thebiaxial drawing process and the thermofixing process, provides thedesirable effect on the thickness unevenness is not known. It is assumedthat such a heat treatment promotes the orientation crystallizationafter the drawing process so as to relax the polymer chain during thethermofixing process and thereby to suppress the thickness unevenness.

[0107] After the film is biaxially drawn, a thermofixing process ispreferably performed. The thermofixing process is performed at atemperature of normally about 150° C. to about Tm, preferably about 155°C. to about Tm. Preferably, a lateral relaxing process is furtherperformed after the thermofixing process. Preferably, a lateral relaxingprocess of about 1% to about 10%, more preferably about 2% to about 8%,is performed at a temperature of about 120° C. to about the thermofixingtemperature.

[0108] As described above, the film may further be laminated into amultilayer film, or subjected to the above-described surface treatment.

[0109] The thickness unevenness in the longitudinal direction of thealiphatic polyester film according to the third aspect of the presentinvention needs to be about 10% or less, preferably about 8% or less,more preferably about 5% or less. The thickness unevenness is expressedas a percentage of the difference between the maximum thickness and theminimum thickness with respect to the average thickness as thethicknesses are measured continuously along the longitudinal directionof the film over a length of, for example, about 3 m. When the thicknessunevenness is excessively large, the film is heated with a film-carryingtension being applied thereof during a process such as a printingprocess or a laminating process. In such a case, the planarity of thefilm varies along the longitudinal direction thereof, and undesirableplanarity may occur, whereby the production yield of the final productis likely to decrease. The film thickness is preferably about 5 μm toabout 50 μm.

[0110] In the third aspect of the present invention, the thermalshrinkage of the aliphatic polyester film at a temperature of about 120°C. in the longitudinal direction needs to be about 5% or less,preferably about 3% or less. When the thermal shrinkage is excessivelylarge, printing misalignment easily occurs in a printing process, andwrinkling easily occurs in a heat seal process.

[0111] The refractive index in the thickness direction (Nz) of thealiphatic polyester film according to the third aspect of the presentinvention is preferably about 1.440 to about 1.455, and more preferablyabout 1.445 to about 1.455. When the value Nz is excessively small, thefilm may easily be ruptured during a film forming process, andwrinkling, planarity deterioration, and the like, may occur during aprinting, laminating or heat seal process, or the like, while the heatseal strength may be poor. When the value Nz is excessively large,planarity deterioration, elongation, or the like, may easily occurbecause the film is heated during a printing, laminating or heat sealprocess, or the like.

[0112] According to the preferred embodiment of the third aspect of thepresent invention, the value (Nx−Ny) obtained by subtracting therefractive index (Ny) in the width direction of the aliphatic polyesterfilm from the refractive index (Nx) in the longitudinal directionthereof is preferably about −0.020 to about 0, more preferably about−0.015 to about 0. When the value Nx−Ny is excessively small, the film,when heated during a printing or laminating process, or the like, isstretched by the film-carrying tension, whereby printing misalignmentand ruffling may easily occur in the printing process, and the planarityis likely to deteriorate. When the value Nx−Ny is excessively large, thethickness unevenness is likely to increase.

[0113] In a preferred embodiment of the present invention, a resin layerhaving a heat seal property, i.e., a sealant layer, is deposited on thealiphatic polyester film. A polyolefin resin, e.g., polypropylene,polyethylene, and the like, is preferably used for the resin layerhaving a heat seal property.

[0114] Fourth Aspect of the Present Invention

[0115] An embodiment of a layered film having a desirable gas barrierproperty according to the fourth aspect of the present invention will bedescribed below.

[0116] In the fourth aspect of the present invention, the oxidevapor-deposited layer may be formed by appropriately using a physicalvapor deposition method such as a vacuum deposition method, a sputteringmethod, or an ion plating method, or a chemical vapor deposition methodsuch as CVD. The method for heating employed may be a resistance heatingmethod, an induction heating method, an electron beam heating method, orthe like. It is also possible to use a reactive vapor deposition methodin which an oxygen gas, a nitrogen gas, a hydrogen gas, an argon gas, acarbonic acid gas, a water vapor, or the like, is introduced as areactive gas, or those employing addition of ozone, an ion assist, orthe like. Alternatively, it is possible to apply a bias voltage acrossthe aliphatic polyester film, as a substrate, or to change conditionssuch as a heating condition, a cooling condition, or the like, underwhich the aliphatic polyester film is deposited depending upon the vapordeposition method used. Similarly, where a sputtering method or a CVDmethod is employed, the material to be deposited, the reactive gas, thealiphatic polyester film bias, the heating or cooling condition for thealiphatic polyester film may be changed to be suitable for the vapordeposition method used. It is also effective to perform, before orduring the vapor deposition, a corona discharge treatment, a flametreatment, a low temperature plasma treatment, a glow dischargetreatment, a reverse sputtering treatment, a surface rougheningtreatment, or the like, on the surface of the aliphatic polyester filmonto which the material is deposited, so as to further improve theadhesion strength of the vapor-deposited layer.

[0117] An aluminum oxide/silicon oxide-based vapor-deposited layer isconsidered to be a mixture of aluminum oxide and silicon oxide and/or amixture containing a compound of aluminum, silicon, and oxygen. Aluminumoxide in the vapor-deposited layer comprises a mixture of variousaluminum oxides such as Al, AlO, Al₂O₃, and the like, and the respectivecontents, etc., of the aluminum oxides vary depending upon the conditionunder which the vapor-deposited layer is applied. Silicon oxide isconsidered to comprise Si, SiO, SiO₂, and the like, and the ratiothereof varies depending upon the condition under which thevapor-deposited layer is applied. The content of the aluminum oxide inthe vapor-deposited layer is about 20 wt % to about 99 wt %, preferablyabout 30 wt % to about 95 wt %. A slight amount (preferably up to about3% with respect to the total component of the vapor-deposited layer) ofone or more other component may be included to an extent such that thedesirable properties of the vapor-deposited layer are retained.

[0118] The aluminum oxide-based vapor-deposited layer is considered tocomprise Al, AlO, Al₂O₃, and the like, and the ratio thereof variesdepending upon the condition under which the vapor-deposited layer isapplied.

[0119] The silicon oxide-based vapor-deposited layer is considered tocomprise Si, SiO, SiO₂, and the like, and the ratio thereof variesdepending upon the condition under which the vapor-deposited layer isapplied.

[0120] The term “specific gravity” as used herein refers to a ratio of aweight of a substance having a certain volume at a certain temperaturewith respect to the weight of a standard substance (water at about 4°C.) having the same volume. Normally, the specific gravity of asubstance can be measured by measuring the weight and volume of thesubstance and calculating the weight ratio thereof with respect to thesame volume of water at about 4° C. However, the volume of anvapor-deposited layer is difficult to measure. Therefore, thevapor-deposited layer may need to be first separated, by stripping itfrom the aliphatic polyester film on which it has been deposited, ordissolving only the aliphatic polyester film from the vapor-depositedfilm, thereby obtaining a film solely of the vapor-deposited layer.Then, a specific gravity measurement method such as those described inJISK7112 is preferably used. For example, in a sink and float method, asample is immersed in a solution having a known specific gravity, so asto determine the specific gravity of the vapor-deposited layer based onthe sinking/floating thereof in the solution. A mixture of carbontetrachloride and bromoform, methylene iodide, or the like, may be usedas the solution having a known specific gravity. The specific gravity ofa sample can also be measured by a density gradient tube method in whicha sample, e.g., a separated film, is immersed in various solutionshaving continuously different density gradients.

[0121] Where an aluminum oxide/silicon oxide vapor-deposited layer isemployed, the “b value” calculated as follows is set to be about 1.6 toabout 2.2, preferably about 1.7 to about 2.0. The b value is calculatedfrom Expression 1 below:

[0122] Expression 1: b=D−0.01A

[0123] where D denotes the specific gravity of the vapor-depositedlayer, and A denotes the weight percent of the aluminum oxide in thevapor-deposited layer. When the b value is excessively small, thestructure of the aluminum oxide/silicon oxide vapor-deposited layer willbe coarse, and the gas barrier property will be insufficient. When the bvalue is excessively large, the initial gas barrier property immediatelyafter the film formation will be desirable, but the film will beexcessively hard, and will have poor mechanical properties,particularly, a poor Gelbo property. Moreover, after the film isdynamically fatigued from repeated bending, etc., for example, the gasbarrier property is significantly reduced, thereby detracting from itsutility as a gas barrier film.

[0124] Where an aluminum oxide-based vapor-deposited layer is used asthe vapor-deposited layer, the specific gravity of the aluminumoxide-based vapor-deposited layer is preferably about 2.70 to about3.30, more preferably about 2.80 to about 3.20. When the specificgravity of the vapor-deposited layer is excessively small, the structureof the aluminum oxide-based vapor-deposited layer will be coarse, andthe gas barrier property will be insufficient. When the specific gravityvapor-deposited layer is excessively large, the initial gas barrierproperty immediately after the film formation will be desirable, but thefilm will be excessively hard, and will have poor flexibility. After thefilm is dynamically fatigued from repeated bending, for example, the gasbarrier property is significantly reduced, thereby detracting from itsutility as a gas barrier film.

[0125] Where a silicon oxide-based vapor-deposited layer is used as thevapor-deposited layer, the specific gravity of the silicon oxide-basedvapor-deposited layer is preferably about 1.80 to about 2.20, morepreferably about 1.90 to about 2.15. When the specific gravity of thevapor-deposited layer is excessively small, the structure of the siliconoxide-based vapor-deposited layer will be coarse, and the gas barrierproperty will be insufficient. When the specific gravity of thevapor-deposited layer is excessively large, the initial gas barrierproperty immediately after the film formation will be desirable, but thefilm will be excessively hard, and the flexibility thereof easilydeteriorates. Thus, the gas barrier property significantly decreasesafter the process, thereby detracting from its utility as a gas barrierfilm.

[0126] It is possible to obtain a gas barrier film having a desirableflexibility by applying the above-described vapor-deposited layer on thealiphatic polyester film.

[0127] A feature of the preferred embodiment is the adjustment of thesurface state of the aliphatic polyester film. That is, according to thepreferred embodiment of the present invention, the three-dimensionalsurface roughness SΔa (the three-dimensional average inclinationgradient) of at least the deposition side of the aliphatic polyesterfilm is adjusted to be about 0.01 to about 0.04, thereby obtaining afilm having a desirable running property during the film processing anda desirable gas barrier property after the film processing. When thevalue SΔa is less than about 0.01, the running property during the filmprocessing will be poor, and the film surface after the film has beenrun will be significantly rough, reducing the gas barrier property. Whenthe value SΔa is more than about 0.04, the transparency and/or theanti-erosion property are likely to be poor, thereby deteriorating thefilm quality.

[0128] In a preferred embodiment, substantially no projection as high asabout 1.89 μm or more exists on the surface of the aliphatic polyesterfilm. When there is a projection which is as high as about 1.89 μm ormore, the transparency is likely to be poor, and the anti-erosionproperty is also likely to be reduced, thereby generating white powder.

[0129] Normally, the thickness of the vapor-deposited layer ispreferably about 10 Å to about 5000 Å. When the film thickness isexcessively small, it is difficult to obtain a sufficient gas barrierproperty. An excessively large film thickness is also impractical,because it is likely to reduce the flexibility and increase theproduction cost, while saturating the gas barrier property, which thencan no longer be improved.

[0130] The aliphatic polyester film with an vapor-deposited layerapplied thereon according to the fourth aspect of the present inventionneeds to be colorless and transparent, so that the contents therein canbe seen therethrough. Therefore, the haze of the deposition film ispreferably low, e.g., about 5% or less.

[0131] On the aliphatic polyester film having the vapor-deposited layerbeing applied thereon, one or more other layer may be formed to anextent such that the object of the invention is realized.

[0132] In a preferred embodiment of the present invention, a resin layerhaving a heat seal property, i.e., a sealant layer, is deposited on thealiphatic polyester film. A polyolefin resin, e.g., polypropylene andpolyethylene, is preferably used for the resin layer having a heat sealproperty.

EXAMPLES

[0133] The present invention will now be described in more detail by wayof illustrative examples and comparative examples which are not intendedto limit the present invention.

[0134] First, evaluations of various properties used in the variousexamples and comparative examples below will be described.

[0135] (1) Three-Dimensional Surface Roughness SRa

[0136] In Example A, the surface roughness of the film was measured witha stylus type three-dimensional surface roughness meter (SE-3AKmanufactured by Kosaka Kenkyusho). First, the surface roughness of thefilm was measured over about 1 mm along the longitudinal directionthereof under conditions including a stylus radius of about 2 μm, a loadof about 30 mg, a cut-off value of about 0.25 mm, and a stylus speed ofabout 0.1 mm/sec. The obtained data was divided into 500 points at about2 μm intervals, and the height at each point was input to athree-dimensional surface roughness analyzer (SPA-11) at a quantizationwidth of about 0.00312 μm. Similarly, the surface roughness of the filmwas measured over about 0.3 mm along the width direction thereof, for150 points at about 2 μm intervals, and the data at each point was inputto the analyzer.

[0137] Each obtained surface roughness curve was approximated to a sinecurve. The average roughness was obtained using a mean roughness planeas a reference plane.

[0138] Specifically, the value SRa as used herein refers to a valueobtained by using the above-described stylus type three-dimensionalsurface roughness meter to measure the heights of the sample film at apredetermined number of measurement positions which are arranged atregular intervals, and processing the measured values by theabove-described three-dimensional surface roughness analyzer.

[0139] A rectangular coordinates system is defined along the meanroughness plane with an X axis and a Y axis as well as a Z axis, whichis defined orthogonal to the mean roughness plane. The value SRa isobtained from a portion of the mean roughness plane having a length Lxalong the X axis, and a length Ly along the Y axis, with an area ofLx×Ly=S_(M), according to the following expression. The obtained valueSRa is expressed in μm.${SRa} = {\frac{1}{S_{M}}{\int_{0}^{Lx}{\int_{0}^{Ly}{{{f\left( {x,y} \right)}}{x}{y}}}}}$

[0140] Herein, Z=f(x,y) denotes a function representing a film surface,i.e., the height Z, at a position (x,y) in the rectangular coordinatessystem as defined above.

[0141] In Example A, the SRa value was calculated according to the aboveexpression, with Lx=500 and Ly=150.

[0142] (2) PCC Value

[0143] In Example A, the number of projections per 1 mm² as high asabout 0.00625 μm or more with respect to a standard surface having astandard height, which was used in the calculation of SRa value, wascounted.

[0144] (3) Haze

[0145] In Examples A and D, the haze was measured by 300A manufacturedby Nihon Seimitsu Kogaku according to JIS-K6714.

[0146] (4) Refractive Index

[0147] In Example A, the refractive index of the film along thelongitudinal thereof was obtained by using Abbe's Refractometer 1Tmanufactured by Atago Co., Ltd.

[0148] In Example B, the refractive index (Nz) of the film along thethickness direction thereof was measured by Abbe's Refractometer 1Tmanufactured by Atago Co., Ltd.

[0149] In Example C, the refractive indices (Nz, Nx, Ny) of the filmalong the thickness direction, the longitudinal direction, and the widthdirection, respectively, were measured by Abbe's Refractometer 1Tmanufactured by Atago Co., Ltd.

[0150] (5) Handling Property of Film

[0151] In Example A, a film wound around a wide roll was slit at a highspeed, and re-wound around a narrower roll. Then, the film was evaluatedinto one of four grades as defined below based on the quality of theobtained roll in terms of the winding misalignment, wrinkling, bubbles,etc.

[0152] Grade 1: Very difficult to obtain acceptable slit roll

[0153] Grade 2: Acceptable slit roll can be obtained at low speed

[0154] Grade 3: Acceptable slit roll can be obtained at medium speed

[0155] Grade 4: Acceptable slit roll can be obtained at high speed

[0156] (6) Adhesiveness Evaluation

[0157] In Example A, about 2 g/m² of an adhesive AD585/CAT-10(manufactured by Toyo Morton) was applied on a surface of each ofbiaxially drawn aliphatic polyester films obtained in various examplesand comparative examples on which a corona treatment has been performed.Then, about 60 μm of an undrawn polypropylene film (P1120 manufacturedby Toyobo Co., Ltd.) was attached thereon by a dry laminate method so asto provide a sealant layer, thereby obtaining a layered product of thebiaxially drawn aliphatic polyester film. The peel strength of theproduct in a dry state and that in a wet state were measured. Themeasurement was conducted by a 90° peel test at a pulling speed of about100 mm/min. In Table A below, “Dry” denotes a value measured at atemperature of about 23° C. and a humidity of about 65%, whereas “Wet”denotes a value measured while the film sample was made wet by drippingwater thereto using a pippet.

[0158] (7) Surface Energy

[0159] In Example B, various wetting index standard solutions(manufactured by Nacalai Tesque Co., Ltd.) were applied on the film overa width of about 1 cm and a length of about 6 cm. Then, a reagent withwhich the film shrinks in about 2 seconds was selected so as to measurethe surface energy.

[0160] (8) Process Suitability

[0161] In Example B, a printing ink layer was provided by printing agravure ink (Lamiace 61 white 2 liquid type manufactured by Toyo InkManufacturing Co., Ltd.) on each of layered thermoplastic films obtainedin various examples and comparative examples. Then, after about 2 g/m²of an adhesive AD585/CAT-10 (manufactured by Toyo Morton) was appliedthereon, about 60 μm of an undrawn polypropylene film (P1120manufactured by Toyobo Co., Ltd.) was attached thereon by a dry laminatemethod so as to provide a sealant layer, thereby obtaining a layeredproduct of the aliphatic polyester film. The quality of each of theobtained layered products was observed and evaluated into one of threegrades as defined below.

[0162] ◯: Good quality

[0163] Δ: Some planarity deterioration observed, but acceptable in termsof wrinkling and printing misalignment

[0164] X: Planarity deterioration observed, and unacceptable in terms ofwrinkling and printing misalignment

[0165] (9) Heat Seal Strength

[0166] In Example B, the peel strength in the dry and wet states of thelayered product as described in (8) above. The measurement was conductedby a 90° peel test at a pulling speed of about 100 mm/min. In Table Bbelow, “Without water” denotes a value measured at a temperature ofabout 23° C. and a humidity of about 65% RH, whereas “With water”denotes a value measured while the film sample was made wet by drippingwater thereto using a pippet.

[0167] (10) Thickness Unevenness Along the Longitudinal Direction

[0168] In Example C, the thickness of the film was measured continuouslyover about 3 m along the longitudinal direction thereof using a “Filmthickness continuous measuring apparatus” manufactured by Anritsu Corp.The thickness unevenness was calculated according to the followingexpression:

[0169] Thickness unevenness (%)=[(maximum thickness−minimumthickness)/average thickness]×100

[0170] (11) Thermal Shrinkage Along the Longitudinal Direction

[0171] In Example C, the film was cut into a piece about 10 mm wide andabout 250 mm long. The piece of film was marked at an about 200 mminterval, and the interval defined by the mark was measured as a value“A” under a constant tension of about 5 g. Successively, the film piecewas placed in an oven, whose atmosphere was at about 120° C. After about30 minutes with no load applied, the film piece was taken out of theoven, and the interval defined by the mark was measured as a value “B”under a constant tension of about 5 g. The thermal shrinkage wasobtained according to the following expression:

[0172] Thermal shrinkage (%)=[(A−B)/A]×100

[0173] (12) Process Suitability

[0174] In Example C, a printing ink layer was provided by printing agravure ink (Lamiace 61 white 2 liquid type manufactured by Toyo InkManufacturing Co., Ltd.) on each of thermoplastic films obtained invarious examples and comparative examples. Then, after about 2 g/m² ofan adhesive AD585/CAT-10 (manufactured by Toyo Morton) was appliedthereon, about 60 μm of an undrawn polypropylene film (P1120manufactured by Toyobo Co., Ltd.) was attached thereon by a dry laminatemethod so as to provide a sealant layer, thereby obtaining a layeredproduct of the aliphatic polyester film. The quality of each film duringthe processes was observed so as to evaluate the process suitabilityinto one of three grades as defined below in terms of wrinkling andprinting misalignment.

[0175] Wrinkling

[0176] ◯: Substantially no wrinkling; good quality

[0177] Δ: Slight wrinkling observed

[0178] X: Planarity deterioration and wrinkling observed

[0179] Printing Misalignment

[0180] ◯: Substantially no printing misalignment; good quality

[0181] Δ: Slight printing misalignment observed

[0182] X: Planarity deterioration and printing misalignment observed

[0183] (13) Film Formation

[0184] In Example C, no or one occurrence of film rupture during threehours of continuous biaxial drawing was considered as good, and two ormore occurrences of film rupture was considered as poor.

[0185] (14) Gas Barrier Property

[0186] In Examples D, E and F, the oxygen permeability was measured byan oxygen permeability measuring apparatus (“OX-TRAN 10/50A”manufactured by Modern Controls) at a humidity of about 0%, atemperature of about 25° C. and a purge interval of about 2 days. Thewater vapor permeability was measured by a water vapor permeabilitymeasuring apparatus (“PERMATRAN” manufactured by Modern Controls) at ahumidity of about 90%, a temperature of about 40° C. and a purgeinterval of about 2 days.

[0187] (15) Oxygen Permeability after Running the Film

[0188] In Examples D, E and F, the film was run at a high speed for along time while pressing it against a metal guide roll. After the guideroll friction test, the oxygen permeability was measured by the methodas described above.

[0189] (16) Oxygen Permeability After Bending Fatigue

[0190] In Examples D, E and F, bending fatigue was applied on the filmusing Gelboflex tester (manufactured by Tester Sangyo Co., Ltd.).According to MIL-B131H, a piece of a sample about 112″×8″ was made intoa form of a cylinder having a diameter of about 3({fraction (1/2)})″,and the sample piece was held at both ends with the initial holdinginterval of about 7″. A twist of about 4000 was applied at an about3({fraction (1/2)})″ stroke. The reciprocating movement was repeated ata rate of about 40 reciprocations/min, at a temperature of about 20° C.and at a relative humidity of about 65%. After the film was fatigued asdescribed above, the oxygen permeability thereof was measured.

[0191] (17) Three-Dimensional Average Inclination Gradient SΔa

[0192] In Examples D, E and F, the surface roughness of the film wasmeasured with a stylus type three-dimensional surface roughness meter(SE-3AK manufactured by Kosaka Kenkyusho). First, the surface roughnessof the film was measured over about 1 mm along the longitudinaldirection thereof under conditions including a stylus radius of about 2μm, a load of about 30 mg, a cut-off value of about 0.25 mm, and astylus speed of about 0.1 mm/sec. The obtained data was divided into 500points at about 2 μm intervals, and the height at each point was inputto a three-dimensional surface roughness analyzer (SPA-11). Similarly,the surface roughness of the film was measured over about 0.3 mm alongthe width direction thereof, for 150 points at about 2 μm intervals, andthe data at each point was input to the analyzer at a quantization widthof about 0.00312 μm. Then, using the analyzer, the value SΔa wasobtained. SΔa denotes a three-dimensional average inclination gradientas defined below.

[0193] SΔa refers to an average inclination gradient across the entirefilm surface. At a plurality of levels parallel to the mean roughnessplane, the number of protrusions of the film and the cross-sectionalarea thereof are obtained so as to calculate the average cross-sectionalarea of the protrusions for the respective levels. The average radius ofthe cross sections of the protrusions for each level is calculated fromthe average cross-sectional area, and a ratio of change in the height tochange in the average protrusion radius is obtained for each level. Theobtained values are further averaged to obtain the value SΔa.

[0194] Specifically, the value SΔa as used herein refers to a valueobtained by using the above-described three-dimensional surfaceroughness meter to measure the heights of the sample film at apredetermined number of measurement positions which are arranged atregular intervals, and processing the measured values by theabove-described three-dimensional surface roughness analyzer. Morespecifically, each obtained surface roughness curve is approximated toasine curve. The resulting data points are combined together so as toobtain three-dimensional data. The inclination gradient across theentire surface is calculated from the number and heights of protrusionswhile using the mean roughness plane as the reference plane.

[0195] A rectangular coordinates system is defined along the meanroughness plane with an X axis and a Y axis as well as a Z axis, whichis defined orthogonal to the mean roughness plane. The value SΔa isobtained from a portion of the mean roughness plane having a length Lxalong the X axis, and a length Ly along the Y axis, with an area ofLx×Ly=S_(M), according to the following expression.${S\quad \Delta \quad a} = {\frac{1}{S_{M}}{\int_{0}^{Lx}{\int_{0}^{Ly}{\sqrt{\left( \frac{\delta \quad f}{\delta \quad x} \right)^{2} + \left( \frac{\delta \quad f}{\delta \quad y} \right)^{2}}{x}{y}}}}}$

[0196] Herein, Z=f(x,y) denotes a function representing a film surface,i.e., the height Z, at a position (x,y) in the rectangular coordinatessystem as defined above.

[0197] In Examples D, E and F, the SΔa value was calculated according tothe above expression, with Lx=500 and Ly=150.

[0198] (18) Number of Projections on the Film Surface

[0199] In Examples D, E and F, aluminum was vapor deposited on a surfaceof the film under vacuum. Using a two-beam interference microscopeprovided with a filter having a wavelength of about 0.54 μm, ringssurrounding a projection were observed. A set of seven or more ringssurrounding a projection (corresponding to a projection height of about1.89 μm or more) was considered as a projection. The number ofprojections (or the number of ring sets) was counted over an area ofabout 1.3 mm², and the obtained count was calculated into the number ofprojections per a unit of area.

Examples A1, A2, A3, and Comparative Examples A1, A2

[0200] About 100 weight parts of L-lactide and about 0.03 weight part oftin octylate as a catalyst were charged in a reaction chamber. Areaction was allowed for about 1 hour while the temperature in thechamber was kept at about 190° C. After the reaction, the obtainedreaction system was depressurized so as to distill off the remainingL-lactide, thus obtaining a polylactic acid. The reduced viscosity ofthe obtained polylactic acid was about 1.9 dl/g. A silica particleaggregate having an average particle size of about 1.8 μm (SYLYSIA 350manufactured by Fuji-Silysia Chemical Ltd.) was used as a slip additive.Various amounts of the slip additive were added in the form of a slurrydispersed in L-lactide before initiating the L-lactide polymerizationreaction. The amounts of slip additive added are shown in Table A below.

[0201] The above-described aliphatic polyester was dried in vacuum atabout 110° C. for about 4 hours using an ordinary method, extruded froma T die at about 200° C., and adhered by a static charge around acasting drum at about 16° C. so as to be rapidly cooled and solidified.Thus, a cast film was obtained. The cast film was heated by a roll whichhas been heated to about 72° C., and then drawn in the longitudinaldirection at a drawing ratio of about 3.3. Then, the drawn film waspre-heated to about 60° C. in a tenter, and drawn in the width directionat a drawing ratio of about 4.0 while being heated to about 75° C., andthermally fixed at about 150° C. Moreover, a lateral relaxing processwas performed at about 150° C. for relaxing the film in the widthdirection by about 3%, thereby obtaining a biaxially drawn aliphaticpolyester film having a thickness of about 12 μm. The characteristicvalues of the obtained drawn films are shown in Table A. The refractiveindex (Nx) of the film along the vertical direction thereof after thevertical drawing process was about 1.469. Each of the films obtained inExamples A1, A2, A3, and Comparative Example A1 had a good transparency,while that obtained in Comparative Example A2 had a poor transparency.

Example A4

[0202] A film was produced in a manner similar to Example A1 except thatabout 0.10 weight part of spherical silica particles having an averagediameter of about 1.65 μm (AMT-silica #100B and AMT-silica #100Bmanufactured by Mizusawa Industrial Chemicals Ltd.) as a slip additive.The results obtained are shown in Table A below. The refractive index(Nx) of the film along the vertical direction thereof after the verticaldrawing process was about 1.467. The obtained film had a goodtransparency.

Comparative Example A3

[0203] A film was produced in a manner similar to Example A1 except thatabout 0.12 weight part of spherical silica particles having an averagediameter of about 5.8 μm (AMT-silica #500B manufactured by MizusawaIndustrial Chemicals Ltd.) as a slip additive. The results obtained areshown in Table A below. The refractive index (Nx) of the film along thevertical direction thereof after the vertical drawing process was about1.467. The obtained film had a poor transparency.

Comparative Example A4

[0204] A film was produced in a manner similar to Example A1 except thatsilica particles having an average particle size of about 7 nm (AEROSIL300 manufactured by Nippon Aerosil Ltd.) were used as an inorganic slipadditive, and Neutron S (manufactured by Nippon Fine Chemical Co., Ltd.)was used as an organic slip additive. The results obtained are shown inTable A below.

Comparative Example A5

[0205] A film was produced in a manner similar to Comparative Example A4except that no organic slip additive was added. The results obtained areshown in Table A below. TABLE A Organic slip Inorganic slip additiveadditive Average Amount added Amount added PCC Adhesiveness particlesize in weight in weight (Projections/ SRa 7000 − Handling Haze (g/15mm) μm part part mm²) μm 45000 * SRa property % Dry/Wet Example A1 1.80.10 0 1350 0.045 4975 4 3.1 308/211 Example A2 1.8 0.20 0 1980 0.0664030 4 6.5 310/190 Example A3 1.8 0.01 0 330 0.018 6190 3 1.8 302/193Example A4 1.65 0.10 0 1750 0.069 3895 4 7.8 305/200 Comparative 1.80.005 0 155 0.008 6640 2 0.9 308/203 Example A1 Comparative 1.8 0.60 03730 0.095 2725 2 14.3 306/198 Example A2 Comparative 5.8 0.12 0 18800.108 2140 3 10.3 303/215 Example A3 Comparative 0.007 0.50 1 600 0.0086640 1 2.2 148/55 Example A4 Comparative 0.007 0.50 0 600 0.008 6640 12.0 290/185 Example A5

Example B1

[0206] About 0.06 weight part of a silica particle aggregate having anaverage particle size of about 1.8 μm was added as a slip additive forforming surface projections to about 100 weight parts of a poly-L-lacticacid having a weight average molecular weight of about 250000, therebyobtaining an aliphatic polyester polymer. The polymer was extruded by anextrusion machine having a T die and a bore diameter of about 30 mm at aresin temperature of about 2100 C. Then, the extruded polymer was cooledby a chilled roll at about 20° C., thereby obtaining an undrawn filmhaving a thickness of about 275 μm. The film was pre-heated to about 95°C. by a plurality of ceramic rolls, and vertically drawn between therolls at a drawing rate of about 30000%/min and at a drawing ratio ofabout 1.4, and further vertically drawn at about 97° C. and at a drawingratio of about 2.5. Then, the film was laterally drawn by a tenter-typedrawing machine at about 100° C. and at drawing ratio of about 4, andthen thermally fixed at about 150° C. Thereafter, a lateral relaxingprocess of about 3% was performed at about 130° C. The obtained film washeated to about 40° C. and subjected to a corona treatment, therebyobtaining a drawn film having a thickness of about 20 μm. The propertiesof the obtained film are shown in Table B below.

Comparative Example B1

[0207] A biaxially drawn film was obtained in a manner similar toExample B1 except that the drawing rate was changed to about 5000%/min.The properties of the obtained film are shown in Table B below.

Comparative Example B2

[0208] A biaxially drawn film was obtained in a manner similar toExample B1 except that the vertical drawing was performed in a singlestage at about 65° C. and at a drawing ratio of about 3.5, without thesecond vertical drawing stage. The properties of the obtained film areshown in Table B below.

Comparative Example B3

[0209] A biaxially drawn film was obtained in a manner similar toExample B1 except that about 0.15 weight part ofN,N′-ethylenebis(stearylamide) was added as a slip additive to about 100weight parts of a polylactic acid. The properties of the obtained filmare shown in Table B below.

Comparative Example B4

[0210] A biaxially drawn film was obtained in a manner similar toExample B1 except that a corona treatment was not performed. Theproperties of the obtained film are shown in Table B below. TABLE BComparative Comparative Comparative Comparative Example B1 Example B1Example B2 Example B3 Example B4 Nz 1.4476 1.4552 1.4380 1.4475 1.4475Film formation Good Good Many Good Good occurrences of rupture Surfaceenergy 51 51 51 38 40 (dyne/cm) Process suitability ◯ Δ X ◯ ◯ Heat sealstrength (g/15 mm) Without water 600 700 400 60 200 With water 500 600300 30 80

Example C1

[0211] About 0.06 weight part of a silica particle aggregate having anaverage particle size of about 1.8 μm was added as a slip additive forforming surface projections to about 100 weight parts of a poly-L-lacticacid (Tg=61.6° C., Tm=170° C.) having a weight average molecular weightof about 250000. The obtained composition was extruded by an extrusionmachine having a T die and a bore diameter of about 30 mm at a resintemperature of about 210° C. Then, the extruded polymer was cooled by achilled roll at about 200 C, thereby obtaining an undrawn film having athickness of about 3000 μm. The film was pre-heated to about 96° C. by aplurality of ceramic rolls, and vertically drawn between the rolls at adrawing rate of about 30000%/min and at a drawing ratio of about 1.5,and further vertically drawn at about 98° C. and at a drawing ratio ofabout 2.7. Then, the film was laterally drawn by a tenter-type drawingmachine at about 80° C. and at drawing ratio of about 3.8, and thenthermally fixed at about 155° C. Thereafter, a lateral relaxing processof about 3% was performed at about 135° C. Thus, a biaxially drawn filmof the present invention having a thickness of about 20 μm was obtained.The properties of the obtained film are shown in Table C below.

Comparative Example C1

[0212] A biaxially drawn film was obtained in a manner similar toExample C1 except that, in the vertical drawing process, the film waspre-heated to about 96° C. by a plurality of ceramic rolls, and the filmwas vertically drawn in a single stage between the rolls at a drawingrate of about 30000%/min and at a drawing ratio of about 2.5, withoutthe second vertical drawing stage. The properties of the obtained filmare shown in Table C below.

Comparative Example C2

[0213] A biaxially drawn film was obtained in a manner similar toExample C1 except that the vertical drawing process was performed in asingle stage at about 68° C. and at a drawing ratio of about 3.5,without the second vertical drawing stage. The properties of theobtained film are shown in Table C below.

Example C2

[0214] A biaxially drawn film was obtained in a manner similar toExample C1 except that the vertical drawing process was performed atabout 12000%/min. The properties of the obtained film are shown in TableC below.

Comparative Example C3

[0215] A biaxially drawn film was obtained in a manner similar toExample C1 except that the thermofixing process was performed at about140° C. The properties of the obtained film are shown in Table C below.

Example C3

[0216] A biaxially drawn film was obtained in a manner similar toExample C1 except that the thermofixing process was performed at about150° C. The properties of the obtained film are shown in Table C below.

Example C4

[0217] A biaxially drawn film was obtained in a manner similar toExample C1 except that after the biaxial drawing process, the film wassubjected to a heat treatment at about 100° C. for about 10 seconds andthen thermally fixed. The properties of the obtained film are shown inTable C below. TABLE C Comparative Comparative Comparative Example C1Example C1 Example C2 Example C2 Example C3 Example C3 Example C4Thickness unevenness (%) 2.2 12.1 13.3 8.5 2.4 2.5 1.5 Thermal shrinkage(%) 2.3 1.9 5.1 2.2 9.8 4.7 2.2 Nz 1.4461 1.4565 1.4394 1.4521 1.44751.4469 1.4463 Nx − Ny −0.0133 −0.0211 −0.0032 −0.0207 −0.0142 −0.0136−0.0130 Process suitability Wrinkling ◯ X X Δ X Δ ◯ Printing ◯ X X Δ X Δ◯ misalignment Film formation Good Good Poor Good Good Good Good

Example D1, and Comparative Example D1

[0218] About 100 weight parts of L-lactide and about 0.03-weight part oftin octylate as a catalyst were charged in a reaction chamber. Areaction was allowed for about 1 hour while the temperature in thechamber was kept at about 190° C. After the reaction, the obtainedreaction system was depressurized so as to remove the remainingL-lactide, thus obtaining a polylactic acid. The reduced viscosity ofthe obtained polylactic acid was about 1.8 dl/g.

[0219] The above-described polylactic acid was dried in vacuum at about110° C. for about 4 hours using an ordinary method, melted and extrudedby an extrusion machine having a T die and a bore diameter of about 30mm at a resin temperature of about 210° C. Then, the extruded polymerwas cooled by a chilled roll, thereby obtaining an undrawn film having athickness of about 300 μm. Then, the film was immediately verticallydrawn by a roll-type drawing machine at about 75° C. and at a drawingratio of about 3.2. The film was then laterally drawn by a tenter-typedrawing machine at about 100° C. and at drawing ratio of about 4.Thereafter, the film was relaxed by about 6% while being thermally fixedat about 150° C. Then, a corona discharge treatment was performed on thefilm, thereby obtaining a drawn film having a thickness of about 25 μm.

[0220] An aluminum oxide/silicon oxide-based vapor-deposited layer wasapplied on the corona-discharge-treated biaxially drawn film using anelectron beam heating-type vacuum deposition apparatus and using a vapordeposition source of Al₂O₃ and SiO₂ in the form of particles having asize of about 3 mm to about 5 mm. The depositing materials, Al₂O₃ andSiO₂, were not mixed together but alternately heated in a time divisionmanner, while dividing the furnace into two chambers by a carbon plate,and using a single electron gun as a heat source. Variousvapor-deposited layers were obtained by adjusting the emission currentof the electron gun and the heating ratio between Al₂O₃ and SiO₂. Afterthe resin layer of the obtained layered film was dissolved, the specificgravity of the aluminum oxide/silicon oxide-based vapor-deposited layerwas measured by the sink and float method.

Example D2, and Comparative Example D2

[0221] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example D1 except that various amounts of asilica particle aggregate having an average particle size of about 1.8μm (SYLYSIA 350 manufactured by Fuji-Silysia Chemical Ltd.) as a slipadditive were added in the form of a slurry dispersed in L-lactidebefore initiating the polymerization reaction. The amounts of slipadditive added are shown in Table D below.

Comparative Example D3

[0222] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example D1 except that various amounts ofspherical silica particles having an average particle size of about 5.8μm (AMT-silica #500B manufactured by Mizusawa Industrial Chemicals Ltd.)as a slip additive were added in the form of a slurry dispersed inL-lactide before initiating the polymerization reaction. The amounts ofslip additive added are shown in Table D below.

Example E1, and Comparative Example E1

[0223] A polylactic acid was obtained by a method similar to the methodof synthesizing a polylactic acid of Example D1.

[0224] A corona-discharge-treated biaxially drawn film was prepared by amethod similar to the method of preparing a corona-discharge-treatedbiaxially drawn film of Example D1.

[0225] A vapor-deposited film was deposited on the obtainedcorona-discharge-treated biaxially drawn film using an electron beamheating-type vacuum deposition apparatus and using a vapor depositionsource of Al₂O₃. Various vapor-deposited layers having variouscompositions were obtained by using a single electron gun as a heatsource while adjusting the emission current and the vapor pressure.After the resin layer of the obtained layered film was dissolved, thespecific gravity of the aluminum oxide-based vapor-deposited layer wasmeasured by a sink and float method.

Example E2, and Comparative Example E2

[0226] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example E1 except that various amounts of asilica particle aggregate having an average particle size of about 1.8μm (SYLYSIA 350 manufactured by Fuji-Silysia Chemical Ltd.) as a slipadditive were added in the form of a slurry dispersed in L-lactidebefore initiating the polymerization reaction. The amounts of slipadditive added are shown in Table E below.

Comparative Example E3

[0227] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example E1 except that various amounts ofspherical silica particles having an average particle size of about 5.8μm (AMT-silica #500B manufactured by Mizusawa Industrial Chemicals Ltd.)as a slip additive were added in the form of a slurry dispersed inL-lactide before initiating the polymerization reaction. The amounts ofslip additive added are shown in Table E below.

Example F1, and Comparative Example F1

[0228] A polylactic acid was obtained by a method similar to the methodof synthesizing a polylactic acid of Example D1.

[0229] A corona-discharge-treated biaxially drawn film was prepared by amethod similar to the method of preparing a corona-discharge-treatedbiaxially drawn film of Example D1.

[0230] A vapor-deposited film was applied on the obtainedcorona-discharge-treated biaxially drawn film using an electron beamheating-type vacuum deposition apparatus and using a vapor depositionsource of Si and SiO₂. The vapor-deposited materials were not mixedtogether, but placed respectively into two divided chambers, andalternately heated in a time division manner, while using an electrongun as a heat source. Various vapor-deposited layers having variouscompositions were obtained by adjusting the emission current and theheating ratio. After the resin layer of the obtained layered film wasdissolved, the specific gravity of the silicon oxide-basedvapor-deposited layer was measured by a sink and float method.

Example F2, and Comparative Example F2

[0231] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example F1 except that various amounts of asilica particle aggregate having an average particle size of about 1.8μm (SYLYSIA 350 manufactured by Fuji-Silysia Chemical Ltd.) as a slipadditive were added in the form of a slurry dispersed in L-lactidebefore initiating the polymerization reaction. The amounts of slipadditive added are shown in Table F below.

Comparative Example F3

[0232] A film with a vapor-deposited layer applied thereon was producedby a method as described in Example F1 except that various amounts ofspherical silica particles having an average particle size of about 5.8μm (AMT-silica #500B manufactured by Mizusawa Industrial Chemicals Ltd.)as a slip additive were added in the form of a slurry dispersed inL-lactide before initiating the polymerization reaction. The amounts ofslip additive added are shown in Table F below.

[0233] In the following tables, “over” denotes that the oxygenpermeability was too large to measure. TABLE D1 Specific gravityComposition of Thickness Oxygen permeability of vapor-depositedvapor-deposited layer of vapor-deposited Number of cc/m² 24 h atm layerAl₂O₃ SiO₂ layer Haze SΔa projections Initial After After bending g/cm³wt % wt % Å % — Projections/mm² value running fatigue Example D1-1 1.8520 80 800 0.4 0.003 0 1.0 1.8 1.3 Example D1-2 1.92 20 80 1000 0.4 0.0030 1.0 2.2 1.5 Example D1-3 2.07 20 80 2000 0.4 0.003 0 0.8 3.6 3.1Example D1-4 2.18 20 80 2000 0.4 0.003 0 0.7 4.1 3.5 Example D1-5 2.3020 80 3000 0.4 0.003 0 0.5 5.0 4.0 Example D1-6 2.01 40 60 700 0.4 0.0030 0.9 1.9 1.2 Example D1-7 2.21 40 60 1000 0.4 0.003 0 0.7 2.2 1.6Example D1-8 2.38 40 60 1000 0.4 0.003 0 0.7 2.4 1.8 Example D1-9 2.4240 60 2000 0.4 0.003 0 0.5 2.4 2.0 Example D1-10 2.55 40 60 3000 0.40.003 0 0.2 3.2 2.5 Example D1-11 2.23 60 40 800 0.4 0.003 0 0.9 2.0 1.5Example D1-12 2.36 60 40 1000 0.4 0.003 0 0.6 2.3 1.7 Example D1-13 2.5260 40 1000 0.4 0.003 0 0.5 2.7 2.0 Example D1-14 2.61 60 40 2000 0.40.003 0 0.3 3.0 2.4 Example D1-15 2.79 60 40 3000 0.4 0.003 0 0.2 3.32.8 Example D1-16 2.55 80 20 1000 0.4 0.003 0 0.8 1.8 1.1 Example D1-172.71 80 20 1000 0.4 0.003 0 0.6 2.1 1.3 Example D1-18 2.89 80 20 10000.4 0.003 0 0.5 2.5 1.7 Example D1-19 2.97 80 20 2000 0.4 0.003 0 0.52.9 1.9 Example D1-20 2.99 80 20 4000 0.4 0.003 0 0.2 3.3 2.3 ExampleD1-21 2.61 95 5 1000 0.4 0.003 0 1.0 1.9 1.3 Example D1-22 2.76 95 52000 0.4 0.003 0 0.8 2.0 1.5 Example D1-23 2.87 95 5 2000 0.4 0.003 00.5 2.3 1.5 Example D1-24 2.99 95 5 3000 0.4 0.003 0 0.5 2.6 1.7 ExampleD1-25 3.13 95 5 4000 0.4 0.003 0 0.3 2.9 2.9

[0234] TABLE D2 Specific gravity Composition of Thickness Oxygenpermeability of vapor-deposited vapor-deposited layer of vapor-depositedNumber of cc/m² 24 h atm layer Al₂O₃ SiO₂ layer Haze SΔa projectionsInitial After After bending g/cm³ wt % wt % Å % — Projections/mm² valuerunning fatigue Comparative 1.65 15 85 1000 0.4 0.003 0 2.4 3.9 3.0Example D1-1 example D1-2 2.38 15 85 2000 0.4 0.003 0 0.8 Over OverComparative 1.90 15 85 1000 0.4 0.003 0 1.8 4.0 3.0 example D1-3Comparative 2.15 15 85 1000 0.4 0.003 0 1.5 3.8 2.8 example D1-4Comparative 1.70 20 80 1000 0.4 0.003 0 2.0 3.6 2.8 example D1-5Comparative 2.45 20 80 3000 0.4 0.003 0 0.5 Over Over example D1-6Comparative 1.88 40 60 700 0.4 0.003 0 1.9 3.4 2.7 example D1-7Comparative 2.65 40 60 3000 0.4 0.003 0 0.2 Over Over example D1-8Comparative 2.15 60 40 800 0.4 0.003 0 1.2 3.0 1.9 example D1-9Comparative 2.93 60 40 3000 0.4 0.003 0 0.3 Over Over example D1-10Comparative 2.38 80 20 1000 0.4 0.003 0 1.0 2.9 1.6 example D1-11Comparative 3.21 80 20 4000 0.4 0.003 0 0.2 Over Over example D1-12Comparative 2.50 95 5 1000 0.4 0.003 0 1.6 3.1 2.0 example D1-13Comparative 3.20 95 5 4000 0.4 0.003 0 0.2 Over Over example D1-14

[0235] TABLE D3 Amount Specific gravity Composition of Thickness ofvapor of slip Number of Oxygen permeability of vapor- vapor-depositedlayer deposited additive projections cc/m² 24 h atm deposited layerAl₂O₃ SiO₂ layer Haze added SΔa projections/ Initial After After bendingg/cm³ wt % wt % Å % wt % — mm² value running fatigue Example D2-1 2.2020 80 2000 2.6 0.08 0.015 0 0.7 3.3 3.2 Example D2-2 2.41 40 60 2000 2.60.08 0.015 0 0.7 2.1 2.0 Example D2-3 2.60 60 40 2000 2.6 0.08 0.015 00.5 2.0 1.9 Example D2-4 2.85 80 20 2000 2.6 0.08 0.015 0 0.5 2.2 2.0Example D2-5 2.21 20 80 2000 4.4 0.16 0.036 0 0.6 2.9 2.8 Example D2-62.43 40 60 2000 4.4 0.16 0.036 0 0.5 2.1 2.0 Example D2-7 2.59 60 402000 4.4 0.16 0.036 0 0.5 1.8 1.8 Example D2-8 2.84 80 20 2000 4.4 0.160.036 0 0.7 2.2 2.1

[0236] TABLE D4 Amount Specific gravity Composition of Thickness ofvapor of slip Number of Oxygen permeability of vapor- vapor-depositedlayer deposited additive projections cc/m² 24 h atm deposited layerAl₂O₃ SiO₂ layer Haze added SΔa projections/ Initial After After bendingg/cm³ wt % wt % Å % wt % — mm² value running fatigue Compalative 1.85 4060 2000 5.0 0.56 0.045 0 2.3 3.0 2.9 Example D2-1 Compalative 2.66 40 602000 5.0 0.56 0.045 0 0.3 Over Over Example D2-2 Compalative 2.14 60 402000 5.0 0.56 0.045 0 2.0 3.3 2.9 Example D2-3 Compalative 2.94 60 402000 5.0 0.56 0.045 0 0.2 Over Over Example D2-4 Compalative 1.84 40 602000 8.0 0.13 0.035 14 2.2 2.6 2.5 Example D3-1 Compalative 2.67 40 602000 8.0 0.13 0.035 14 0.4 Over Over Example D3-2 Compalative 2.12 60 402000 8.0 0.13 0.035 14 2.2 2.9 2.8 Example D3-4 Compalative 2.95 60 402000 8.0 0.13 0.035 14 0.3 Over Over Example D3-5

[0237] TABLE E1 Specific gravity Oxygen permeability of vapor-depositedThickness of Number of cc/m² 24 h atm layer vapor-deposited layer HazeSΔa projections Initial After After bending g/cm³ Å % — Projections/mm²value running fatigue Example E1-1 2.72 500 0.3 0.004 0 1.9 2.9 2.0Example E1-2 2.88 500 0.3 0.004 0 1.7 3.0 2.1 Example E1-3 2.97 500 0.30.004 0 1.6 3.2 2.2 Example E1-4 3.05 1000 0.3 0.004 0 1.6 3.3 2.4Example E1-5 3.11 1000 0.3 0.004 0 1.4 3.3 2.4 Example E1-6 3.01 20000.3 0.004 0 1.2 3.4 2.6 Example E1-7 3.06 2000 0.3 0.004 0 1.1 3.5 2.7Example E1-8 3.14 3000 0.3 0.004 0 1.0 3.7 2.7 Example E1-9 3.20 30000.3 0.004 0 1.0 4.0 2.9 Example E1-10 3.29 3000 0.3 0.004 0 0.9 4.2 3.0

[0238] TABLE E2 Specific gravity Oxygen permeability of vapor-depositedThickness of Number of cc/m² 24 h atm layer vapor-deposited layer HazeSΔa projections Initial After After bending g/cm³ Å % — Projections/mm²value running fatigue Compalative 2.72 500 0.3 0.004 0 1.9 2.9 2.0Example E1-1 Compalative 2.65 1000 0.3 0.004 0 2.4 6.7 6.3 Example E1-2Compalative 3.35 3000 0.3 0.004 0 0.8 Over Over Example E1-3 Compalative3.40 3000 0.3 0.004 0 0.7 Over Over Example E1-4

[0239] TABLE E3 Specific gravity of vapor- Thickness of Oxygenpermeability deposited vapor-deposited Amount of slip Number of cc/m² 24h atm layer layer Haze additive added SΔa projections Initial AfterAfter bending g/cm³ Å % wt % — Projections/mm² value running fatigueExample E2-1 3.02 1000 2.7 0.09 0.018 0 1.2 2.6 2.5 Example E2-2 3.051000 4.9 0.18 0.038 0 1.1 2.5 2.7 Compalative Example E2-1 2.63 500 13.00.56 0.044 0 2.4 6.5 6.2 Compalative Example E2-2 3.38 3000 13.6 0.560.042 0 0.8 Over Over Compalative Example E3-1 2.65 500 11.0 0.13 0.03914 2.3 7.0 6.8 Compalative Example E3-2 3.39 3000 10.6 0.13 0.038 10 0.9Over Over

[0240] TABLE F1 Specific gravity Oxygen permeability of vapor-depositedThickness of Number of cc/m² 24 h atm layer vapor-deposited layer HazeSΔa projections Initial After After bending g/cm³ Å % — Projections/mm²value running fatigue Example F1-1 1.80 500 0.3 0.005 0 1.7 2.7 1.7Example F1-2 1.85 500 0.3 0.005 0 1.6 2.7 1.7 Example F1-3 1.92 500 0.30.005 0 1.6 2.8 1.7 Example F1-4 1.97 1000 0.3 0.005 0 1.4 3.0 1.8Example F1-5 2.01 1000 0.3 0.005 0 1.0 3.2 2.0 Example F1-6 1.98 20000.3 0.005 0 0.8 3.5 2.2 Example F1-7 2.02 2000 0.3 0.005 0 0.8 3.6 2.2Example F1-8 2.05 3000 0.3 0.005 0 0.7 3.8 2.4 Example F1-9 2.13 30000.3 0.005 0 0.7 3.8 2.5 Example F1-10 2.20 3000 0.3 0.005 0 0.7 4.0 3.1

[0241] TABLE F2 Specific gravity Oxygen permeability of vapor-depositedThickness of Number of cc/m² 24 h atm layer vapor-deposited layer HazeSΔa projections Initial After After bending g/cm³ Å % — Projections/mm²value running fatigue Comparative 1.73 500 0.3 0.005 0 2.4 4.8 4.5Example F1-1 Comparative 1.78 1000 0.3 0.005 0 1.9 6.8 4.8 Example F1-2Comparative 2.25 3000 0.3 0.005 0 0.8 Over Over Example F1-3 Comparative2.30 3000 0.3 0.005 0 0.6 Over Over Example F1-4

[0242] TABLE F3 Specific gravity of vapor- Thickness of Oxygenpermeability deposited vapor-deposited Amount of slip Number of cc/m² 24h atm layer layer Haze additive added SΔa projections Initial AfterAfter bending g/cm³ Å % wt % — Projections/mm² value running fatigueExample F2-1 3.02 1000 2.7 0.09 0.018 0 1.2 2.6 2.5 Example F2-2 2.011000 2.8 0.08 0.019 0 1.0 2.0 2.1 Example F2-2 2.02 1000 4.8 0.16 0.0370 1.0 1.9 2.0 Compalative Example F2-1 1.78 500 13.2 0.56 0.044 0 2.44.5 4.3 Compalative Example F2-2 2.31 3000 13.4 0.56 0.042 0 0.8 OverOver Compalative Example F3-1 1.77 500 10.8 0.13 0.039 12 2.3 6.9 6.5Compalative Example F3-2 2.32 3000 10.2 0.13 0.038 11 0.9 Over Over

[0243] According to the present invention, it is possible to obtain abiaxially drawn aliphatic polyester film having desirable handlingproperty, transparency and adhesiveness, which is suitable for packagingapplications, and the like.

[0244] The aliphatic polyester film of the present invention has adesirable suitability for processes such as printing and laminatingprocesses, which is an important practical property of a packaging film.The aliphatic polyester film also has a desirable heat seal strengthafter being made into a bag. Thus, the present invention provides a veryuseful and environment-friendly general packaging film.

[0245] The aliphatic polyester film of the present invention has adesirable process suitability, and does not undergo a change indimension or wrinkling during processes such as printing and laminatingprocesses. This is an important property of a packaging film for usewith fresh food, processed food, drugs, medical devices, electronics, orthe like. Moreover, the aliphatic polyester film of the presentinvention does not undergo planarity deterioration or printingmisalignment, thus being very useful as a general packaging film.

[0246] According to the present invention, it is possible to obtain agas barrier film which has desirable transparency, flexibility, runningproperty during the film processing, and gas barrier property after thefilm has run through a film processing machine while being in contactwith a part thereof, which are important properties required in ageneral packaging film.

[0247] Various other modifications will be apparent to and can bereadily made by those skilled in the art without departing from thescope and spirit of this invention. Accordingly, it is not intended thatthe scope of the claims appended hereto be limited to the description asset forth herein, but rather that the claims be broadly construed.

What is claimed is:
 1. A film comprising, as its main component, analiphatic polyester whose primary repeating unit is represented by ageneral formula —O—CHR—CO— (where R denotes H or an alkyl group having acarbon number of 1-3), wherein: a three-dimensional surface roughnessSRa of at least one side of the film is about 0.01 μm to about 0.1 μm;and PCC value denoting the number of projections on the film per a unitof area along a mean roughness plane and the three-dimensional surfaceroughness SRa satisfy the following relationship: PCCvalue≦7000-45000×SRa.
 2. A film according to claim 1, wherein the PCCvalue is about 1000/mm² or more.
 3. A film according to claim 1, whereinthe aliphatic polyester is a polylactic acid.
 4. A film comprising, asits main component, an aliphatic polyester whose primary repeating unitis represented by a general formula —O—CHR—CO— (where R denotes H or analkyl group having a carbon number of 1-3), wherein: a refractive index(Nz) in a thickness direction thereof is about 1.440 to about 1.455; anda surface energy of the film is about 45 dyne/cm or more.
 5. A filmaccording to claim 4, further comprising a resin layer having a heatseal property.
 6. A film according to claim 5, wherein the resin layerhaving a heat seal property comprises a polyolefin resin.
 7. A filmaccording to claim 4, wherein the aliphatic polyester is a polylacticacid.
 8. A film comprising, as its main component, an aliphaticpolyester whose primary repeating unit is represented by a generalformula —O—CHR—CO— (where R denotes H or an alkyl group having a carbonnumber of 1-3), wherein: a thickness unevenness along a longitudinaldirection of the film is about 10% or less; and a thermal shrinkagealong the longitudinal direction at about 120° C. is about 5% or less.9. A film according to claim 8, wherein: a refractive index (Nz) along athickness direction of the film is about 1.440 to about 1.455; and thethermal shrinkage along the longitudinal direction at about 120° C. isabout 3% or less.
 10. A film according to claim 9, wherein a value(Nx−Ny), which is obtained by subtracting a refractive index (Ny) in awidth direction of the film from the refractive index (Nx) in thelongitudinal direction thereof, is about −0.020 to about
 0. 11. A filmaccording to claim 8, wherein a weight average molecular weight of thealiphatic polyester is about 10000 to about
 500000. 12. A film accordingto claim 8, wherein the aliphatic polyester is a polylactic acid.
 13. Agas barrier film, comprising a resin layer and a vapor-deposited layerwhich is applied on at least one side of the resin layer, wherein: theresin layer comprises, as its main component, an aliphatic polyesterwhose primary repeating unit is represented by a general formula—O—CHR—CO— (where R denotes H or an alkyl group having a carbon numberof 1-3); the vapor-deposited layer is selected from the group consistingof an aluminum oxide/silicon oxide-based vapor-deposited layer, analuminum oxide-based vapor-deposited layer and a silicon oxide-basedvapor-deposited layer; a content of aluminum oxide in the aluminumoxide/silicon oxide-based vapor-deposited layer is about 20 wt % toabout 99 wt %; a “b” value, which is calculated according to thefollowing expression (1) based on a specific gravity D of thevapor-deposited layer and the aluminum oxide content A in wt % in thevapor-deposited layer, satisfies the following expression (2):Expression (1): b=D−0.01A Expression (2): 1.6≦b≦2.2 (where D denotes thespecific gravity of the vapor-deposited layer, and A denotes thealuminum oxide content in wt % in the vapor-deposited layer); a specificgravity of the aluminum oxide-based vapor-deposited layer is about 2.70to about 3.30; and a specific gravity of the silicon oxide-basedvapor-deposited layer is about 1.80 to about 2.20.
 14. A film accordingto claim 13, wherein: a three-dimensional surface roughness SΔa (athree-dimensional average inclination gradient) of at least thedeposition side of the resin layer is about 0.01 to about 0.04; andsubstantially no projection as high as about 1.89 μm or more exists onat least the deposition side of the resin layer.
 15. A film according toclaim 14, wherein: a thickness of the resin layer is about 10 μm toabout 250 μm; and a thickness of the vapor-deposited layer is about 10 Åto about 5000 Å.
 16. A film according to claim 14, wherein the aliphaticpolyester is a polylactic acid.